While less frequent than in the era before effective treatment for hypertension, hypertensive emergency remains a relatively common cause of hospital admission in some sub-populations. Hypertensive emergency accounts for approximately 60 admissions per year to the Medical Service in our hospital, or about one percent of Medical Service admissions, and a somewhat higher proportion of intensive care unit admissions and utilization. The importance of hypertensive emergency may be underestimated because ICD discharge codes include only malignant hypertension, a severe form comprising only about half of the admissions for hypertensive emergency. There have been almost no epidemiologic studies of hypertensive emergency in the past 20 years, and very little is known about risk factors. The overall goal of this study is to gain knowledge necessary to plan preventive strategies targeted at populations at high risk. Specific aims are to test the hypotheses that hypertensive emergency is associated with (1) non-compliance with antihypertensive medications. (2) low level of contact with the medical care system. (3) alcohol abuse, and (4) cigarette smoking: and (5) to describe the clinical characteristics and long-term prognosis of patients hospitalized with hypertensive emergency including the morbidity, mortality, and cost, and the extent to which hypertensive emergency occurs among previously diagnosed and treated hypertensives rather than among unscreened and undiagnosed hypertensives. Aims 1-4 will be accomplished through a matched case-control study design, while Aim 5 will be accomplished through description and follow-up of the case series. Cases will be obtained from admissions to the Medical Service at Presbyterian Hospital. Controls will be selected from emergently hospitalized or emergency room patients with admitting diagnoses or presenting complaints restricted to conditions not known to be associated with alcohol abuse, cigarette smoking, or other hypothesized risk factors. Our preliminary studies indicate that subject accrual is feasible and suggest that hypertensive emergency is almost entirely preventable. This study addresses the questions of who is at risk for hypertensive emergency and why current hypertension control strategies fail to prevent hypertensive emergency more fully.